ELECTROACTIVATED PURIFICATION OF MINERALIZED WATERS

Abstract

One of the main problems of the integrated processing of sea, groundwater or mine water when receiving drinking water is their high salinity, as well as mineral and biological deposits in the pro-cesses of demineralization. Several methods for demineralization of water: evaporation, reagents, membranes (reverse osmosis), ion exchange, electrodialysis, etc. have been developed.
Each of these methods has both positive and negative qualities and is used within certain concentration limits. New developments offer complex multistage mine water treatment schemes with concentrated brine processing. The reduction of CO32-, SO42-, Cl- ions from 25000 to 1000 mg/dm3 is the most sophisticated component of salt extraction technology. These processes are very time consuming and energy intensive. In addition, methods such as electrodialysis, reverse osmosis, sodium cationization are economically feasible to apply with mineralization of 1000-100 mg/dm3 and below. The urgent task is to create an apparatus for primary demineralization of highly mineralized mine water with minimization of energy costs. The method of unipolar electrochemical activation in the purification and desalination of water provides a short-term state of the aqueous solution, when the cathode and anode electrolysis process-es have changed its composition, and the processes of mutual neutralization of electrolysis products are artificially restrained by the presence of permeable membranes-partitions, which are temporarily electrodeparticles. At the cathode, a concentration gradient of hydroxyl ions is observed:2 H2O + 2 e → 2 OH- + H2. At the anode acidification of the electrolyte occurs: 2 H2O - 4 e → 2 H + + 2O2. In the cathode space, due to the increased concentration of free hydroxyl ions, secondary processes of fixation of hydroxides of a number of metals, the cations of which form OH-insoluble bases and basic salts, are observed. The article deals with the methods of groundwater treatment – their advantages and disadvantages. The investigations carried out experimentally have proved the versatility of the method of electrochemical activation of water, which allows to reach the required desalination standards in one process, while reducing the content of organic compounds and (due to the synthesis of ClO- ions) to produce metered water chlorination. The catholyte and anolyte, after pre-extracting the precipitates formed, are mixed for another demineralization step (e.g. reverse osmosis). It is found that the unipolar electrical activation method is effective for mineralized waters con-taining carbonates, sulfates and chlorides of calcium, magnesium, iron and other heavy metals. Chlorine ion, as shown by the experiments on the treatment of sodium chloride solution, leads to the for-mation of water desirable ClO- and ClO3- ions, which prevent the clogging and biofouling of membranes. Several semi-industrial devices have been developed and studies of the efficiency of the method of electroactivation have been carried out, dependences of parameters of electrochemical influence on the composition of highly mineralized and groundwater have been determined. Graphic dependences of the degree of water purification on various parameters (current, voltage, distance between electrodes, time of electro-activation, volume of acid water sampling during electro-activation) are obtained, their analysis is made and conclusions are drawn regarding the use of electrochemical activation process for the preparation of water supplied to stage of membrane desalting.